Metabolic component of the temperature-sensitivity of slow waves recorded from gastric muscle of the guinea-pig

Abstract

The effects of changes in temperature on slow waves were investigated in smooth muscle tissues isolated from the guinea-pig gastric antrum. Within the range 24°C to 42°C, elevation of temperature increased the frequency and maximum rate of rise of the upstroke phase (dV/dt) of slow waves and decreased their duration, with no alteration to amplitude or resting membrane potential. These observations also applied to follower potentials and pacemaker potentials recorded from longitudinal muscle and myenteric interstitial cells, respectively. Slow waves were comprised of 1st and 2nd components, and the latency for generating the 2nd component was decreased exponentially by elevating temperature, reaching a stable value of about 1 s above 32°C. The temperature coefficient was >2 for the frequency, dV/dt and latency of the 2nd component, about 1.7 for the duration and about 1 for amplitude. Potassium cyanide (KCN), an inhibitor of mitochondrial metabolic activity, reduced the frequency and duration of slow waves, with no alteration to other parameters (amplitude, dV/dt, latency). In the presence of 30 μM KCN, the temperature-dependency of the frequency of slow waves was diminished or abolished, while other parameters of slow waves remained unaltered. These results indicate that in slow waves the frequency may be related to metabolic activities, while the temperature-dependent changes in the dV/dt, latency for the 2nd component and duration of slow waves are produced largely by mechanisms other than metabolic activity.

Factors which determine the duration of follower potentials in longitudinal smooth muscle isolated from the guinea-pig stomach antrum

“…These values were comparable to those reported previously by Dickens et al (1999) and Nakamura et al (2006). The I-D relationship was measured in all preparations, and one of the typical examples was shown in Fig.…”

“…Isolated gastric smooth muscle generates slow waves in circular muscle cells or follower potentials in longitudinal muscle cells, in response to pacemaker potentials generated in ICC-MP (Dickens et al, 1999;Dickens et al, 2001). The occurrence of individual pacemaker potentials is not constant, and it is a function of temperature, membrane potential and activities of intracellular components such as endoplasmic reticulum (ER) and mitochondria (Nose et al, 2000;Ward et al, 2003;Ward et al, 2004;Nakamura et al, 2006;Suzuki et al, 2006;Kito and Suzuki, 2007;Nakamura et al, 2009). The duration of pacemaker potential is also not homogeneous, and it is shown by Hirst and Edwards (2001) that in smooth muscle segments isolated from the guinea-pig stomach, the duration of driving potential (equal to pacemaker potential) is a function of time required for the generation of the potential after termination of the previous potential, i.e., there is a linear relationship between the time for the interval between pacemaker potentials and the duration of subsequently generated pacemaker potential.…”

Gastric emptying of liquid and solid meals at various temperatures

“…This peristaltic contraction has been demonstrated to be influenced by temperature. A reduction in temperature decreases the propagation rate of slow waves [40], and an increase in temperature increases the frequency and maximum rising rate of the upstroke phase in experimental animals [41]. In a human study, Sun et al [1] found that cold (4°C) or hot (50°C) meals caused the suppression of antral pressure waves and the acceleration of isolated pyloric pressure waves.…”

Factors modifying the frequency of spontaneous activity in gastric muscle

“…The frequency of slow waves is very sensitive to changes in temperature, a high temperature coefficient ( Q 10 ) for slow waves has been reported in the guinea‐pig stomach (Ohba et al 1977; Tomita, 1981; Nakamura et al 2006). The duration, rate of rise of the upstroke phase and frequency of slow waves all show marked temperature sensitivity ( Q 10 > 2; Fig.…”